Hydraulically operated compressor



y 7, 1957 o. J. SCHEMMEL 2,791,370

HYDRAULICALLY OPERATED COMPRESSOR Filed Jan. 22, 1954 4-Sheets-Sheet 1 y1957 v o. J. SCHEMMEL 1 2,791,370

HYDRAULICALLY OPERATED COMPRESSOR Filed Jan. 22, 1954 4 Sheets-Sheet 2 zP fi May 7, 1957 o. J. SCHEMMEL HYDRAULICALLY OPERATED COMIZRESSOR 4Sheets-Sheet 3 Filed Jan. 22, 1954 Ja g y 7, 1957 o. J. SCHEMMEL2,791,370

HYDRAULICALLY OPERATED COMPRESSOR Filed Jan. 22, 1954 4 Sheets-Sheet 47/3 112 r PUMP O EIIJMP 110 117 5 v nite tates Patent HYDRAULICALLYOPERATED COMPRESSOR ()tto I. Schemmel, Chicago, Ill.

Application January 22, 1954, Serial No. 405,599

3 Claims. (Cl. 230-53) The present invention is directed to a powertranslating device, and is primarily concerned with an improvedhydraulically operated compressor.

A compressor built according to the present invention finds particularuse in the field of refrigeration, particularly in refrigeration and airconditioning equipment designed for installation in automobiles andtrucks. In such installations, it is necessary to provide a compact,readily portable unit which can be operated at high elficiency from aportion of an internal combustion engine.

An object of the present invention is to provide an improved powertranslating device, and more specifically, an improved hydraulicallyoperated compressor mechanism.

Another object of the invention is to provide a readily portablecompressor unit particularly adapted for refrig eration systemsassociated with motor driven vehicles.

Still another object of the invention is to provide a highly efi'icient,compact compressor unit, and to provide such a unit with a dual drivesystem whereby the compressor may be operated from an internalcombustion engine or from a secondary source of power.

The meaning and importance of this stated object will be betterunderstood from the following explanation:

Refrigerated trucks of that type in which the refrigerating operation isproduced by the use of the heat cycle, necessarily include in theirequipment power driven compressors for compressing and liquifying therefrigerant which is then cooled by suitable means such as airradiators, and thereafter expanded in the expansion unit to produce therefrigerating action. The present invention concerns itself especiallywith an improved form of such power driven compressor. The arrangementis such that during normal operation on the road the power needed to runsuch compressor is derived from the power plant of the refrigeratedtruck. It is however, highly desirable to be able to operate therefrigerating compressor to produce the desired cooling effect while thetruck is laying over for extended intervals at terminals or delivery orloading stations. In many cases, also, it is desirable to pre-cool therefrigerated space prior to loading, so that time may be saved after theloading operation has been completed, or, in some cases to refrigeratethe loaded space prior to starting the travel of the truck with itsload. In all such cases the needed refrigerating action is producedwhile the truck is standing idle.

When provision is made only for operation of the refrigerationcompressor by power derived from the trucks power plant it is evidentthat it would be necessary to keep the trucks power plant in operationduring such layover or loading or unloading intervals. Since the amountof power needed for operation of the refrigerating compressor is only asmall percent of the capacity of the trucks power plant it is evidentthat the operation of the trucks power plant only for therefrigerating'action, and for extended intervals of time, would be ahighly inefficient and consequently expensive operation. Additionally itwould entail needless operation and wear of the trucks power plant. Theoperation of the internal combustion engine of the trucks power plantwhile standing within an enclosed space, such as a station or terminal,also presents elements of danger to health, as well as fire hazards,etc.

It is also noted that when the truck is of that type including aso-called tractor unit to which the truck body is removably connectedduring normal road running, the detachment of such body from the tractorunit, as is generally done during extended layovers, makes the tractorpower plant unavailable as a source of power for refrigeration at suchtimes.

To meet the foregoing and like conditions, it has been a widely adoptedpractice to drive the refrigerating compressor by a small speciallyprovided internal combustion engine. Such arrangements present manyobjections from installation as well as operational standpoints. The useof electric motor drives for such truck refrigerating compressors, usingcurrent from the trucks storage battery has been proposed. This scheme,however presents the serious objection that operation of therefrigerating compressor by battery current alone, for an extendedinterval of ten to fifteen hours, or more, in a terminal station wouldentail the provision of battery capacity far beyond the normalrequirements for truck operation, with corresponding high first cost andthe need of carrying a very large dead load during truck travel. It isalso pointed out that even should it be decided to use such electricmotor drive for the refrigeration compressor, operating it off of theusual truck power motor driven electric generator during normal roadrunning operations, such electric motor compressor could not be directlyfed with electricity from the available electricity service supplies atthe terminals in order to avoid operation off of the trucks battery.This is true since the usual truck battery and electrical equipment aredesigned for six or twelve volt or similar low voltage D. C. operation,whereas the usual electricity services are of either or volt A. C.rating.

Accordingly it is a prime object and feature of the present invention toprovide a refrigeration compressor unit and system of operation which isadmirably adapted to meet the normal road running operating conditionsof the refrigerated truck, as well as the very special conditionsimposed during the refrigerating operation when the truck is standingidle for an extended time at a terminal or other station. To this end Ihave provided a refrigeration compressor unit which includes a motordriven by oil under pressure and driving the compressor elements bywhich the refrigerant is compressed. The truck system includes this unitand also suitable piping connections for supply of the oil underpressure from a pumping source and return of the low pressure oil to thepumping source. During normal road operation the pressure and return oillines are connected to a specially provided oil pump which is driven bythe trucks power motor, as by a belt drive from the fan belt shaft; or,alternatively, such pressure and return oil lines may be connected tothe pressure and return sides of the oil pump of the trucks power engineitself. In case of provision of such special oil pump it may be readilyaccommodated under the engine hood. I then also provide a supplementaryelectric motor driven oil pump, having its pressure and return oil linesconnected to the pressure and return oil lines for the oil drivenrefrigerant compressor, under proper valve control so that therefrigerant compressor may be operated by pressure oil supplied eitherby the trucks engine oil circulating system and returned to such systemfor re-circulation, or by such special belt driven pump, for normal roadrunning conditions; or so that the refrigerant compressor may beoperated by pressure oil supplied by such electric motor driven oil pumpand returned to such pump for repeated re-circulation. Suchsupplementary electric motor driven oil pump may be provided with anelectric motor of the A. C. type, intended for operation on the usual10-115 volt A. C. service supply which is almost universally available.

By my novel arrangement outlined above it is possible to use the powersupply available in the conventional form of truck power plant fornormal road operation, and substantially without change of costly orobjectionable na ture. It is also possible to switch over to lay overrefrigerating operation by merely plugging an electric line from thesupplementary electric motor driven oil pump into any available serviceoutlet socket at the terminal or other layover point.

A further description of the present invention will be made inconjunction with the attached sheets of drawings which illustrate apreferred embodiment of the invention.

Figure 1 is a view in elevation and partially in cross sectionillustrating a hydraulically operated compressor embodying theprinciples of the present invention;

Figure 2 is a fragmentary cross-sectional view, with parts in elevation,of the control mechanism employed in the compressor, this view beingtaken substantially along the line 2-2 of Figure 4;

Figure 3 is a cross-sectional view, with parts in elevation, takensubstantially along the line 3--3 of Figure 4;

Figure 4 is a cross-sectional plan view taken substantially along theline 4-4 of Figure 2;

Figure 5 is a fragmentary back view, with parts in elevation, of thecompressor unit;

Figure 6 is a front elevational view of a modified form of theapparatus;

Figure 7 illustrates somewhat schematically the manner in which thecompressor unit may be driven selectively from an internal combustionengine and from an outside source of power;

Figure 8 illustrates schematically the hydraulic control systemillustrated in Figures 1-5 of the drawings; and

Figure 9 is a view in perspective of a truck equipped with a compressorunit of the type described.

In Figure 1, reference numeral 10 indicates generally a metallic casingwhich includes a space serving as a sump or oil reservoir 11. A housing12 is secured to the casing 10 by means of bolts 13 extending throughflange portions 14 of the housing 12.

The bolts 13 are received in a flange portion 16 provided on a secondhousing 17 which encloses the operating members of the hydraulicallycontrolled operating system.

The housing 12 may be provided with spaced fins 19 along its outerperiphery to aid in dissipating heat from the assembly.

The housing 12 is suitably machined to provide a plurality of cylinders21 and 22 which receive a pair of hollow pistons 23 and 24 in slidingengagement. The pistons 23 and 24 may be provided with usual pistonrings 26 as shown in Figure 1.

Secured to the top of the housing 12 is a cover plate 27 which receivesa pair of outlets 28 and 29 in threaded engagement, to direct thecompressed air or other fluid from the cylinders into the mechanismswith which the compressor is associated. It will be understood that thehousing 12 is also provided with, inlet means and valves for directingthe fluid into the cylinders 21 and 22 at the appropriate time duringthe travel of the pistons 23 and 24 to obtain adequate compression ofthe air during the piston strokes.

Each of the pistons 23 and 24 has wrist pins 31 and 32 extendingtherethrough, the wrist pins receiving a pair of rods 33 and 34,respectively. Also secured tothe wrist pins 31 and 32 are a pair ofracks 36 and 37. Disposed between the racks 36' and 3.7 and arranged tobe driven by movement of the racks is a pinion 38 secured to a shaft 39.One end of the shaft 39 is journalled for rotation in 4 i a bearing 40.The rotation of the shaft 39 by the reciproeatory movement of thepistons controls the operation of the hydraulic system, as willhereinafter appear.

The rods 33 and 34 are slidably received in a pair of sleeves 41 and 42,respectively, the sleeves being threaded into suitable recesses providedin the base of the housing 17.

The hydraulic control mechanism is perhaps best illustrated in Figures 2to 4 of the drawings, and as illustrated, the system may include areciprocating valve member 44 having a pair of ports 46 and 47 extendingtherethrough. The valve member 44 is recessed centrally and is machinedto provide a plurality of teeth 48 which are arranged to mesh with theteeth of a pinion 49 fixedly secured to a shaft 51.

The pinion 49 also meshes with a plurality of teeth 52 formed in a slidemember 53, as best illustrated in Figure 2. This slide member 53operates the valve mechanisms, as will be explained more fully.

A pair of vertically extending passageways 56 and 57 are formed in thehousing 17 below the sleeve 41 and a similar set of passageways 58 and59 are formed in the housing below the sleeve 42. When the valve member44 is in the position illustrated in the drawings, the passageway 56communicates with a horizontally extending bore 61 through the port 46.A second horizontally extending bore 62 is arranged to communicate withthe passageway 57, wherrthe valve member 44 is shifted to the right, asviewed in Figure 2. Similarly, a pair of horizontally extending bores 63and 64 are associated with the passageways 58 and 59 of the other halfof the mechanism. In the illustrated position of the valve member 44,the bore 63 communicates with the passageway 58 through the port 47.When the valve member 44 shifts, the port 47 establishes communicationbetween the bore 64 and the passageway 59.

As best illustrated in Figures 2 and 3, the hydraulic fluid, which willnormally be oil, is introduced into one of a pair of inlet lines 66 and67 disposed at opposite ends of the casing. The oil entering through theinlet 66. flows past a compressed helical spring 69 into a horizontallyextending port 71, and then through an angularly disposed passageway 72which connects the port 71 with bore 61 (see Figures 3 and 5).Similarly, a second horizontally disposed port 74 and an angularlydisposed passageway 76 direct oil into the bore 64.

Referring to Figure 3, it will be seen that the hydraulic control systemalso includes a. valve member having a tapered valve seat 77 which isnormally urged into seating relation with the end of a cylinder 78 bythe action of the spring 69. The valve element also includes a rod 79'on which a collar 80 is secured.

Asrthe pistons 23 and 24 are reciprocated, the valve will be openedandclosed once during each reciprocatory cycle. The valve member 77 is.unseated at the time that the piston 23 is at its lowest verticalposition. In this position, an operating pin 81 secured to an arm 82extending from the rack 36 engages the pin 79 and forces the collar 80into a position where it closes off a drain port 83 leading, back to theoil reservoir. The oil, however, is able to flow past the valve seat 77into a conduit 84 and through a port 86 (Figure 2) to thereby supply oilunder pressure against one end of the slide member 53.

The piston 24 has an identical operating mechanism including-1a pin 87which is arranged to open and close a similar valve element in theopposite end of the assembly. The valve is opened and closed by theaction of a second. operating pin 88 secured to an arm 89 extending fromthe. rack 37. When the pin 87 is depressed, the oil under pressure flowsto the opposite side of the slide 53 through a port 91 and communicateswith a conduit 92 (Figures land 4).

The operation of the device shown in Figures 1 to 5 has been simplifiedsomewhat in the schematic showing of Figure 8. The showing in thatfigure represents the position of the assembly at the time that thepiston 23 is commencing to rise and the piston 24 is going down. In thisposition, oil under pressure enters through the line 66, causing oil toflow through the passageways 71, 72, and 61 through the port 46 in thesliding valve member 44, into the passageway 56 and then to the base ofthe rod 33 which is associated with the piston 23. At the same time, oilis being forced out of the other half of the compressor, the piston 24and the rod 34 forcing the oil from the sleeve 42 through the passageway58, the port 47 in the valve 44, and into a drain leading to thereservoir.

During the time the piston 23 is near its lowermost position, the valve77 is unseated, thereby closing off the drain 83 and permitting oil flowthrough the passage 86 against the end of the slide member 53. Duringthis interval, oil is discharged from the opposite end of the slidemember 53 through the outlet passage 91.

Oil is continuously introduced in this manner until such time as thepiston 23 reaches the upper position of its stroke and the piston 24reaches its lowest position. When this occurs, the actuating pin 88depresses the oper ating pin 87, so that oil commences to be dischargedfrom the left side of the slide member 53 as viewed in Figure 8. At thistime, the difference in pressure on opposite sides of the slide member53 causes the slide member 53 to commence moving to the left, as seen inFigure 8. The rotation of the shaft 51 by the movement of the slidemember 53 in engagement with the pinion 49 shifts the position of theslide valve 44 into a position where oil under pressure is introducedinto the sleeve 42 to raise the piston 24, and oil is discharged fromthe sleeve 41 as the piston 23 goes down.

An alternative form of the invention makes use of gearing to translatethe vertical movement of the pistons into the horizontal movement of thereciprocatory valve member 44. In this form of the invention, thehydraulic control system is substantially eliminated, except for thepinion 49, the slide valve member 44 and the slide member 53.

The gearing is best illustrated in Figure 6 of the drawings whichillustrates a relatively small gear 94 secured to the shaft 39 uponwhich the pinion 38 is located, and an idler gear 96 meshing with thegear 94. The idler gear 96 meshes with a larger gear 97 which floats onthe shaft 51. Secured to the gear 97 are a pair of stop pins 98 and 99arranged to engage a finger 101 keyed or otherwise fixedly secured tothe shaft 51.

The gears 96 and 94 are also interconnected by an assembly whichincludes a pin 102 pivotally supported at the gear 97 by a pivot pin103. The pin 102 is slidably received within a rotatable nub 104 mountedon the gear 96. A helical spring 106 extends between the pin 103 landthe nub 104.

From Figure 6 it will be seen that the gear 97 is rotated in acounterclockwise direction by rotation of the gear 96 in a clockwisedirection. The spring 106 is compressed until it reaches anover-the-center position, and at that time, the spring 106 expands,causing the stop pin 98 to strike the finger 101 and thereby rotate theshaft 51 on which the pinion 49 is located. This movement of the pinion49 shifts the reciprocating valve member 44 from one position to itsother position thereby reversing the flow of the hydraulic fluid betweenthe cylinders. in effect, there is provided a lost motion connectionbetween the movement of the pistons and the slide member 44.

Figures 7 and 9 illustrate one manner in which the compressor assemblyof the present invention can be employed for refrigeration systems intrucks. As shown in these two figures, a compressor unit 110 may beconnected across a discharge line 111 and return line 112 of a pair ofpumps 113 and 114 operating in parallel. The pump 113 is arranged to bedriven by an electric motor 115 as shown in Figure 7. The pump 114, onthe other hand, is arranged to be driven from a pulley 116 and a belt117 extending from a source of power on the internal combustion engine,such as the fan belt drive.

For convenience, the engine operated pump 114 may be located immediatelyadjacent the engine as shown in Figure 9 and the electrically drivenpump 113 with the motor may be enclosed in a box readily accessible fromthe outside of the truck. Hence, it becomes a relatively simple matterto drive the compressor from the electrically driven pump 113 when thetruck is in a garage by merely extending power lines to the motor 115.

From the foregoing it will be appreciated that the present inventionprovides a relatively simple, compact compressor unit particularlysuitable for use in refrigeration systems for trucks. The unit needsvery little maintenance and is highly efficient when compared to othertypes of compressors.

It will be evident that various modifications can be made to the abovedescribed apparatus without departing from the scope of the presentinvention.

I claim:

1. A pumping unit including in combination a pair of main cylindershaving floors, a plunger reciprocably mounted in each cylinder, a rockelement, means to journal said rock element for rocking movement,connections between the rock element and both plungers, said connectionsbeing constituted for simultaneous reciprocating movements of theplungers in their cylinders in opposite directions towards and from thefloors of the cylinders, conduits in communication with each cylinderadjacent to the floor thereof, a pressure fluid supply conduit, 21 fluidrelease conduit, a main valve casing having a valve space, areciprocable main valve member reciprocable in said valve space betweena first position and a second position, pressure fluid and release fluidpassages between the pressure fluid supply conduit and the fluid releaseconduit respectively and said main valve casing space, cylinder fluidpassages between the conduits of each cylinder and said main valvecasing space, there being fluid passages in said reciprocable mainvalve, said passages of the main valve and the points of connection ofthe pressure fluid supply passage and the fluid release passage With thevalve casing space, and the points of connection of the cylinderpassages of the two cylinders with said valve casing space, being sorelated that when the main valve is in said first defined position thecylinder passage of one cylinder is in communication with the pressurefluid passage only, and the cylinder passage of the other cylinder is incommunication with the release fluid passage only, and that when themain valve is in said second defined position the cylinder passage ofthe first defined cylinder is in communication with the release fiuidpassage only, and the cylinder passage of the second defined cylinder isin communication with the pressure fluid passage only, together withmeans to reciprocate the main valve synchronously with thereciprocations of the plungers in the cylinders, said means comprising areciprocable main-valve-actuator, a cylindrical space wherein saidmain-valve-actuator is reciprocably mounted, valve actuator fluidpassages individually in fluid connection with the end portions of saidcylindrical space, a valve chamber for each actuator fluid passage andin fluid connection with such passage, each such valve chambercorresponding to one of the main cylinders first mentioned, pressurefluid and release fluid ports in fluid connection with each such valvechamber, the pressure fluid ports communicating with the pressure fluidsupply conduit and the release fluid ports communicating with the fluidrelease conduit respectively, a reciprocable valve member in connectionwith each valve chamber and including a valve element for the pressurefluid port of such chamber and a valve element for the release fluidport of such chamber, each such reciprocable valve member beingconstituted for sealing non-engagement of its release fluid port valveelement with the fluid release port of such valve chamber when itspressure fluid valve element is in sealing engagement with such pressurefluid port of such valve chamber, spring means normally urging each suchvalve member to position to engage the pressure fluid valve element intosealing engagement with the pressure fluid port of such valve chamberand with the release fluid port valve element of such valve member insealing non-engagement with the fluid release port of such valvechamber, actuating means in connection with each plunger for actuatingengagement with the reciprocable valve member of the valve chambercorresponding to such plunger, each such actuating means beingconstituted for actuating movement of such valve member against the urgeof its spring during reciprocating travel of such plunger during the endportion of the plunger reciprocating movement at one end of thereciprocating travel of such plunger in its cylinder, and means to reciprocate the main valve member synchronously with the reciprocations ofthe main-valve-actuator.

2. Means as defined in claim 1, wherein the valve element for thepressure fluid port comprises a poppet type valve, and wherein the valveelement for the release fluid pprt comprises a slide type valve, andwherein said valve elements are spaced and proportioned to produceopening of the release fluid port prior to seating of the poppet typevalve against the pressure fluid port, and wherein spring means normallyretains the valve member in 'position with its poppet type valve elementsealed against the pressure fluid port, and with its slide type valveelement in non-sealing position with respect to the release fluid port.

3. Means as defined in claim 1, wherein the means to reciprocate themain valve member synchronously with the reciprocations of themain-valve-actuator comprises opposing rack elements on the main valvemember and on the main-valve-actuator, together with a pinion meshingwith both said rack elements, and means to journal said pinion forrotation about a fixed axis.

References Cited in the file of this patent UNITED STATES PATENTS385,981 Wellens July 10, 1881 595,429 Alberger Dec. 14, 1897 2,026,479Logan Dec. 31, 1935 2,050,886 Hatmaker Aug. 11, 1936 2,550,678 DeaconMay 1, 1951 FOREIGN PATENTS 512,864 Germany Nov. 20, 1930

